Cowled dome liners



March 7, 1961 L. .1. PIERCE ETAL cowLED DOME LINERs Filed oct. 2s, 1955 Lowell Jackson Pierce, Melrose, and John Albert Benson, l

Nahant, Mass., and Edward Vernon Jaramillo, Des Moines, lowa, assignors to General Electric Company,- a corporation of New York Y v t Fixed oct. 26, 195s, ser. No. 542,809

s claims. (c1. en -39.65)l

The present invention relates to an improved inner gion and uniform air penetration into the primary combustion zone. v

A further object is the provision of an improved inner liner for a combustion system which provides stable and liner for combustion systems and more particularly to a f cowled dome liner for `a higher combustion intensity, straight through, combustion system of the type usually associatedrwith gas turbine engines.

In cannular type combustion systems it has been common practice to provide cross tubes between adjacent liners so that cross ignition occurs permitting essentially instantaneous combustion in all liners. 'In addition, secondaryair is directed around the Vdome of thealiners and mixed with the products ofcombustion to quench the hotgases. One, of the major problems in4 this type combustion system'has been the tendency of the liners to buckle and crackaround thecross tubesandin the dome region' surrounding the primary combustion zone,

thus reducing the average liner life. This problem has v its origin in the fact that as the secondaryfair flows around the ,crosstubes decreased static pressures-'are created in that vicinity according to Bernoullis Theorem. The lower static pressures cause decreased air penetration into the liner around the cross tubes and often resultVV in tiame being forced out of the linerrrinto the secondary air passage. Therefore, the cross tubes in the past always tended to krun hot around the attachment to the liner. This periodic heating and subsequent cooling produced expansion and contraction ofthe cross tubes which caused ,n

fatgueand eventual failure infthe metal ofthe liner resultinginthe formation of large holes at thejpointof attachrnentf'of4 the cross tubes to the'liner; In addition, the decreased;` penetration iof the coolingairiover certain areas of the/ dome caused-these; areas to -become hotter than the rentaind'r of thedome,`thu,s developing internal i stresses'wh'ch'resulted"in buclclingancl crackin oi the domemx'@ t The preseritinvention overcomes the ,disadvantages fof thepriorfknowndevices and increasesthe average'linger ofthe liner andinsuring uniforr'air penetrationfinto the' receive primary airhaving a relatively good velocity profile, thus assuringa proper distribution of air on all sides of the'liner; The cross tubes' are attached tothe cowl and extend through. an opening in thev liner into the primary combustion zone, the edgesof theV opening making sliding contact with the cross' tubes. A transition wall connects the primary and secondary zones of the liner and adds rigidity and strength to the liner.v This transition wall is cooled by a lm of air from the cowl which prevents burning of the transition section.

' t An object ofthe present invention is the provisionV of means for extending the average life of an inner liner in j section.

,-lifebyjremoyingthe-thermal stressesrom the hotnietal eicient combustion and uniform turbine inlet tempera ture distribution. I

Other objects and many of the attendant advantages of this invention will be readily appreciated ,as the same becomes better understood by reference to the following Ydetailed description when considered in connection' with the accompanying drawings wherein:

Fig. l is an elevation view in longitudinal section oa cowled dome liner according to thepresent invention;

Fig. 2 is a sectional view at an enlarged scale of the transition section between the primary and secondary zone of the present invention; and

Fig. 3 is a sectional view taken along line 3-3 of tFig. 1.

Referring more particularly to Fig. 1 of the drawing, the improved inner liner shown therein consists in essence of a dome 11 which defines the primary. combustion zone, a secondary or mixing section 12, a transition wall 13 between the dome and the secondary region, and a cowl. 14 surrounding the dome. A fuel nozzle'lS is received within the opening 16 at theapex of the dome111. A plurality of openings are provided in the vwallioi the, liner surrounding the Yprimary combustion vzone'andare arranged in three bands 17, 18, and 19fabout the periphery of the liner. Louvres 21 are positioned inthe wall ofA the liner between adjacent openings .of the bands 17., 18, and 19. In addition, other louvres such ats-22 are so positioned inthe dome to insure etective air penetration over the entire .area of vthe dome. The secondaryregion 12 is a generally cylindrical section-having a number of bands of openings 23 positioned in the walls thereof. As in the domefregion, the louvres 24 are interspersed between adjacent openings fof some ofthe bands23. The cowl.1'4 extends around'the `entire primary .combustion..zone and is attached-tati -its .trailing ledge 'to the .secondaryt portion -at the transition An opening 25 is. formed in the' dome to re'- ceive the cross Vtube 26.V AsillustratediufFigQ 3, the

edgs .of' the opening 25ar'e` bent outwardly to form an t opening 28 are; likewiseturned outwardly to define an annular flange 29. An angular collar 3b is affixed tothe flange 29. A peripheral flange 31 is provided on tlievexterior of` the ycross tubexand'bearsyagainst the collarft). :The crosstube. isretained within the openings VZSfarid 28 y by means of a clamp (not shown) which locks the llange 31 and the collar 30 together. The leading edge or snout 32 of the cowl is of reduced size and extends upstream into the diffuser 33. The entire liner may be mounted'on one wall of the combustion chamber 34 by means of the bracket 35.

The transition wall 13, as shown in Fig. 2, is an annular member having two parallel` flanges 36 and 37 joined by an intermediate portion 38. The intermediate portion is perforated as at 39 at close intervals near the flange 36. The trailing edge 41 of the dome is bent outwardly as shown, overlying the perforations 39 and defining an annular slot 42 which opens outwardly away from the dome.

In theoperation of the present device Vthe leading edge or snout of the cowl extending upstream into the diffuserl receives primary air before a poor velocity profile can develop. This primary air is directed into the plenum chamber formed by the cowl, the dome and the transition wall. A uniform positive static pressure is thus produced around the entire primary combustion zone forcing the primary air through the louvres and the bands of openings. This uniform positive pressure Vassures uni form air penetration over the entire dome which results in uniform combustion throughout the primary combustion zone. The uniform combustion results in stable continuous burning, thus heating the entire ,dome evenly and causing uniform turbine inlet temperature distribution. The air from the diffuser 33 which is not picked off by the leading edge of the cowl becomes c ooling or secondary air and flows around on the outside of the cowl and then through the openings 23 and the louvres 24 into the secondary region 12 where it mixes with and quenches the hot gases from the primary combustion zone. Primary air, in addition to being forced into the primarv combustion zone, is discharged through the perforations 39 in the transition wall into the annular slot 42 and thence out into the secondary region. The air from the perforations fills the annular slot and then iiows .out over the upturned edge 41, forming a film of cooling air over the intermediate member 38 and the flange 37 of the transition wall. The combustion gases flowing from the primary combustion zone into the secondary region form a vortex at the point of discharge from the combustion zone, creating an additional flame holder at this point and thereby burning the liquid fuel in the cooling boundary air film from the primary zone, resulting in an increase in combustion eiciency. The film of'cooling air over the intermediate portion and the rearward flange prevents destruction of the transition wall by the ame holding in this region. The remainder of the liner is cooled by the primary or` secondary air which enters through the louvres 21, 22, and 24 and forms a thin film over the interior of the liner. `A cross tube 26 is received in the opening 28 and secured to the cowl 14, such that it extends through the opening 25 into theprimary combustion zone. Since the cross tube is secured to the cowl and makes only sliding contact with the flange 27 of the dome, any stresses caused by the periodic heating and subsequent cooling of the cross tube aretransmitted to the relatively cool cowl instead of to the intensely hot dome. Since the cowl is relatively cool itis much more resistant to fatigue from the oscillations caused by the temperature changes in the cross tubesVand has a much longer life under these conditions than would the dome which is subjected to intense heat.

While a particular embodiment of the invention has been illustrated and described, it will be obvious to those adapted to be positioned in said chamber, said liner comprising: a dome section defining the primary combustion zone, said dome having a plurality of openings therein; a cowl spaced from and surrounding the dome, said cowl having a protruding snout portion extending upstream into the diffuser to receive primary air having a good velocity profile; an annular wall extending between the dome and the cowl, the space bounded by the dome, the annular wall and the cowl forming a plenum chamber for the equalization of primaryl air pressure over the entire outer surface of the dome; a mixing section having a larger diameter than said dome, said mixing section being connected to said cowl; and means carried by the dome for directing cooling air across the wall to prevent burning thereof.

2. For use in a combustion system including a combustion chamber and a diffuser, a cowled dome liner adapted to be positioned in said chamber, said liner comprising: a dome section defining the primary combustion zone, said dome having a plurality of openings therein; a cowl spaced from and surrounding the dome, said cowl having a protruding snout portion extending upstream into the diffuser to receive primary air having a good velocity profile; an annular wall extending between the dome and the cowl, the space between the dome, the annular wall and the cowl forming a plenum chamber for the equalization of primary air pressure over the entire outer surface of the dome; a mixing section having a larger diameter than said dome, said mixing section being connected to said cowl; and cooling means to prevent burning of the annular wall, said cooling means including a plurality of openings in the wall and an annular slot defined in part by the trailing edges of the dome.

3. A cowled dome liner for use in a combustion system comprising: a dome section defining the primary combustion zone; a cowl surrounding the entire dome, said cowl being spaced from the dome to provide a plenum chamber therebetween, means on said cowl supplying primary air having a good velocity profile to said plenum chamber; a mixing section connected to the cowl; an annular ,wall forming the downstream end of the plenum chamber, said wall including an intermediate portion spanning the distance between the dome and the mixing section; and cooling means to prevent burning of the wall, said cooling means including a plurality of openings in the interme- Adiate portion and an annular slot formed by the intermediate portion and the trailing edge of the dome.

References Cited in the file of this patent Great Britain '-.v. Sept. 16, 1953 

